Automatically detachable flashless nozzle for rockets



May 13, 195 E. B. BRADFORD ET AL 2,596,644 Q,

AUTOMATICALLY DETACHABLE FLASHLESS NOZZLE FOR ROCKETS Filed Dec. 10,1946 3 Sheets-Sheet l awuc rwom Elilj t IELEIuELfu-mi Alfred AfricunmBlure I113 E N. Hickman y 1952 E. B. BRADFORD ET AL AUTOMATICALLYDETACHABLE FLASHLESS NOZZLE FOR ROCKETS Filed Dec. 10, 1946 3Sheets-Sheet 2 Elimi B. EIELdTEEITIfl.

AlfTE E1 .A'fliEDTLEI I: lurEI'LmE N Hickman.

y 1952 E. B. BRADFORD ET AL 2,596,644

AUTOMATICALLY DETACHABLE FLASHLESS NOZZLE FOR ROCKETS Filed Dec. 10,1946 3 Sheets-Sheet 3 [1111:0511 r: E N Hitzkmun Patented May 13, 1952UNITED STATES PATENT OFFICE AUTOMATICALLY DETACHABLE FLASHLESS NOZZLEFOR ROCKETS retary of War Application December 10, 1946, Serial No.715,298

20 Claims. 1

This invention relates to jet reaction devices, particularly to jetreaction devices of the rocket projectile type useful especially formilitary purposes.

The jet reaction device of this invention consists mainly of acylindrical housing forming a a motor combustion chamber and containingwithin its interior a propellent material such as a double-base powdercomposed of nitroglycerin and nitrocellulose. This propellent materialis combustible to generate a hot propellent fluid under pressure. Thereis secured to the motor chamber, preferably at its rear end, a nozzlewhich provides for a high velocity exit of the propellent fluid.

The rockets of this invention are also characterized by the fact thattheir free-flight burning time is but a small fraction of the total timeof free flight. As a consequence, it has been impracticable prior tothis invention to provide a large nozzle for expanding the gases toobtain a maximum propulsion efficiency, because the increase in velocityobtained by the increase in expansion is more than offset by theincrease in air resistance drag produced by the large nozzle.Consequently, in prior designs it has been the practice to utilize anozzle which is more or less of a compromise between propulsion andaerodynamic eiiiciency.

The nozzle which is described above and which is utilized in thisinvention is essentially a steadyflow device in which there results anexchange in the form of energy of the flowing fluid, from internalpressure energy to kinetic energy. It has been demonstrated bytheoretical analysis and confirmed by experiment that the angle of exitflare of the nozzle is not particularly critical between 8 and 32 totalincluded angle, and in practice we have preferred to remainsubstantially within these limitations. Consequently',if the flare angleis small the length of the nozzle must be considerably increased overprior designs if a sufficient volume is to be provided for the gases toattain the desired expansion. Furthermore, since it is frequentlydesirable to fire these rocket-s from a projector tube, the maximumdiameter of the nozzle is limited to the over-all diameter of therocket. There is, therefore, a limit in the amount the gases may beexpanded.

The rockets of this invention must also be stabilized in free flight. Ithas been the practice prior to this invention to utilize folding finsand to secure these fins to the nozzle at its end. This folding finassembly of prior constructions further limited the maximum nozzlediameter and the 2 amount of expansion. In the fln assembly of thisinvention the nozzle is extended beyond the fins.

In order to improve the propulsion and aerodynamic efliciencies ofrockets, this invention provides means by which the advantages of largenozzles, that is, those having terminal diameters approaching thediameter of the motor chamber or even equaling it, could be utilizedwithout lessening the areodynamic efiiciency of the rocket in freeflight. In accordance with this invention this objective is attained byproviding a rocket motor in which the nozzle thereof is so constructedand attached to the main body of the projectile that after the burningof the rocket propellent has been completed, the nozzle willautomatically separate from the rocket body. This dropping away of thenozzle materially reduces the drag of the rocket and improves itsaerodynamic efiiciency in free flight towards its objective. By virtueof this construction it is possible to utilize a large nozzle forexpanding the gases to a higher degree than was practical heretofore toobtain better propulsion efiiciencies.

5 The inherent areodynamic disadvantages of such large nozzles areavoided in this invention by gases emitted from the open end of thenozzle do not ignite upon contact with the atmosphere. Accordingly, theflash and luminous flame heretofore inherent in the operation of suchrockets is substantially eliminated.

The prior art is replete with so-called flashless propellants, many ofthem contain as the flash inhibitor metallic salts such as potassiumnitrate, barium nitrate, etc., while others may contain hydrocellulose,abietates, etc. Most of these added ingredients have some effect onreducing flash when the propellant is used in guns' Fut their effect ishardly discernible in jet propelled devices where burning continues totake place after the projectile has left the confines of its projectortube. We have discovered, however, that when the nozzle has a relativelylarge diameter at its rear end, preferably a diameter not less than ofthe over-all diameter of the motor chamber, the flash reducingconstituents of the propellant become much more effective. If the flashreducing constituent is potassium nitrate, which is a preferredconstituent, it is believed that the potassium nitrate serves as anoxidizing agent and provides the oxygen necessary to complete thecombustion of the gases in their expansion in the nozzle. It is believedthat this accounts for the fact that the application of this inventionprovides a nearly fiashless jet reaction device, but we do not wish tobe bound by the theory presented herein.

Accordingly, it is an object of this invention A further object of thisinvention is to provide a rocket projectile having a nozzle permitting ahigh degree of expansion of thepropellent fluid but whose ballisticproperties are not detrimentally affected by such nozzle.

Another object of this invention is to provide an improved nozzleconstruction for a rocket projectile characterized by the fact that suchnozzle is automatically detachable from the projectile upon completionof flow of propellant fluid therethrough.

A particular object of this invention is to provide a substantiallyflashless jet reaction device.

The specific nature of this invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawings in which:

Fig. 1 is a fragmentary elevational view in a longitudinal section of arocket motor combustion'chamber and nozzle assembly;

Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. 1;

Fig. 3 is an enlarged partial view of Fig.1 showing the method ofsecuring the nozzle to the combustion chamber;

Fig. 4 is an enlarged view of the fin supporting arm of Fig. l; a t

Fig. 5 is an elevational view in section of a preferred modification ofthe structure shown in Fig. 1;

Fig. 6 is an end view of Fig. 5;

Fig. 7 is a longitudinal view in section of a modification employingfixed fins; and

Fig. 8 is an end view of Fig. 7.

Referring now to the drawings, and more particularly to Fig. 1, therocket comprises a generally cylindrical body member 1 defining acombustion chamber and having a rearwardly inwardly flared entrance I 1leading to a constricted throat [2 of a nozzle l3. The nozzle I3 isactually formed of two parts, a separately formed rearwardly,outwardlyfiared exit l4 and the constricted throat l2 integrally formedwith the combustion chamber. It should be understood, however, that theterm nozzle utilized includes that portion of the steady-flow devicewhich expands the gases without necessarily excluding the throatportion. In other words, it is contemplated that the nozzle may besecured to the motor combustion chamber at any one of a number ofpoints. In any event, that portion of the nozzle which is permitted tofall free of the rocket motor may or may not include the throat.

As illustrated in Fig. 1, the interior surface of the motor chamber atthe end to which the nozzle flare H is secured is undercut to provide ashoulder l and a flat contact surface 16 (Fig. 3). The throat end of thenozzle is cut away in a complementary manner and the wide contactsurline-up of the two parts.

within combustion chamber faces l6 and I6 of the motor and nozzlerespectively may be machined to insure accurate Surfaces I6 and 16 eachhave a groove I! and I! cut therein, as shown in Fig. 3, to provide arecess into which a, low melting point metal l8 may be flowed when thetwo parts are assembled for the purpose of holding the parts firmlytogether. Drilled open- .ings l9 are provided in the nozzle leading togroove II to facilitate filling such groove with the low melting pointmetal [8.

A plurality of pairs of radially projectingrear- 'wardly extending arms22 are welded in spaced relationship to the periphery of the rocketmotor combustion chamber as shown in Fig. 2, so that fins 2| may bepivoted between these arms. Suitable strengthening or reinforcing may beemployed, consistent with good practice and design, to furtherstrengthen and support arms 22; and

the construction must, of course, be such as to maintain fins 2| open inthe position'shown at the bottom of Fig. 1 while in free flight, but asthese details are well known in the art and form no part of ourinvention, they are not shown in the drawing, which is purely schematicas regards the fin assembly. The advantage of the construction shown inFigs. 1 and 2 is that the arms 22 protect the fins from being bent orother wise damaged in shipment or rough handling. These arms also givean added fin surface area which aids in stabilizing the flight of therocket and finally the arms provide lateral support for nozzle l3. Byvirtue of this construction, it is possible to extend the nozzle pastthe'fin assembly to provide for a maximum nozzle diameter.

A suitable double-base propellant 25 is mounted I0 and retained thereinby a cage trap 26. Propellant 25 preferably consists of cylindricalgrains formed of nitroglycerin, nitrocellulose, and a flash reducingagent such as potassium nitrate. The cylindrical grains are providedwith a single axial and concentric perforation by which the grains aremounted on the cage trap 26.

In operation, the passage of the hot gases of combustion through thenozzle liquefy the solder or low melting point metal I 8 after a timeinterval which is determined by the design of the joint. In some designsthis metal which serves to hold the two parts of the nozzle together maybe melted before the burning of the propellant has been completed. Thiswill not adversely affect the operation of the rocket however, becausethe reaction of the expanding high velocity gases upon the flaredsurfaces [4 will force the nozzle up tight against the tubular body tmember so that the nozzle will not be dropped clear of the tubular bodymember until after the burning has been completed and the flow ofpropellent gases stopped. As soon as the burning is completed, therearwardly directed forces produced by the airedrag offered by thenozzle exceed the now-spent reaction forces of the propellent gases, sothat the nozzle will be pulled free of its connection with thecombustion chamber. The deceleration of the nozzle will be greater thanthe deceleration of the rocket motor per se .and as a result the nozzlewill fall behind the rocket motor in free flight. Thus the ballisticproperties of the projectile during its free flight will not beadversely affected by the large diameter nozzle. Furthermore, thecombination of the large diameter nozzle plus the potassium nitrateflash inhibitor produce a burning of the propellant which issubstantially free from flash.

In Figs. 5 and 6v there is shown a modifled construction of the nozzleassembly wherein a ring 3| is threaded to the exterior of theconstricted portion of the tubular member I defining motor combustionchamber for supporting a flared hemispherical member 38 and finsupporting arms 32. The hemispherical member 38 tends to streamline theair flow past the rear portion of the projectile and is instrumental inmaterially reducing the drag caused by that portion of the combustionchamber which is inwardly flared to form the nozzle throat. A rin 36 ofstreamlined cross-section is securedto the rear ends of arms 32 andfolding fins 331arepivotally mounted to the end portions of arms 32.These folding fins are preferably mounted between the respective arms 32and a parallel bracket member 34 which is suitably secured to ring 36.The nozzle cone 35 is secured to the combustion chamber In by being softsoldered at its forward end to the rear end of the tubular member 1.

One of the advantages of the construction of Figs. and 6 is that theflaring of the hemispherical end member 38 not only reduces the dragoffered by the rocket but streamlines the air flow so as to makeeffective use of the fin area of arms 32 whereby greater stability inflight is obtained. Operation is identical to that described inconnection with the arrangement shown in Fig. 1, the nozzle cone 35being dropped at the end of the propellent fluid flow. The propellantutilized in this modification is the same as that provided in themodification of Fig. 1 and preferably contains potassium nitrate as aflash inhibitor. It should be noted that the arms 32 and ring 36 providelateral support for nozzle cone 35.

The modification disclosed in Figs. 7 and 8 differs from that of Figs. 5and 6 in that a ring type fin 40 is substituted for the pivoted fins 33and the ring 36. Ring fin 40 is suitably secured, as by spot welding, tothe rear ends of arms 32. The propellant utilized in this modificationis the same as that provided in the modification of Fig. 1 andpreferably contain massium ni;

as a flash inhibitor. It should be not'iitfiat arms'32 and fin ring!!!provide lateral support for nozzle cone 35.

The modification of Figs. 7 and 8 is particularly well adapted for useon rockets designed to complete their burning within the projector tube,because with the design here disclosed, if the burning continued whilethe rocket was in free flight, the active fin area would be insufficientto stabilize the rocket and the pocketed effect formed between the ringfin 40 and the nozzle cone 35 would produce considerable drag.

It should be understood in all modifications disclosed that the nozzlemay be dropped away by any other method and the invention is not limitedto that disclosed. 7

We claim:

1. In a jet propelled device the combination including a tubular memberdefining a cylindrical combustion chamber containing a materialcombustible to generate a hot propellent fluid under pressure, saidtubular member having an inwardly flared passage leading to aconstricted exit orifice at the rear end thereof, a separately formedVenturi-like nozzle having an...outwardly flared exit passage extendingfrom the constricted portion thereof, and means for securing said nozzleto said tubular member at said exit orifice to expand said propellentfluid flowing through said orifice to a lower temperature and pressure,said nozzle being extended a distance suflicient to substantially reducethe flash occurring on secondary ignition of said fluid upon dischargefrom said nozzle, said securing means including a metal having',arelatively low melting point operative in response to combustion of saidmaterial for releasing said nozzle from said tubular member.

2. In a jet propelled device, the combination including a tubular memberdefining a combustion chamber adapted to contain a material combustibleto generate a propellent fluid under pressure, a separately formednozzle for exchanging the energy form of the propellent fluid, bondingmeans securing said nozzle to said tubular member communicating withsaid chamber, said bonding means including a metal having a relativelylow melting point for rendering said bonding means inefiective upon theapplication of heat at. a temperature below that generated in thecombustion" chamber during normal operation thereof," whereby saidnozzle is freed from said tubular member upon combustion thereof.

3. In a jet propelled device the combination including, a tubular memberdefining a combustion chamber adapted to contain a propellent materialcombustible to generate a hot propellent fluid under pressure, aseparately formed nozzle, means securing said nozzle to said tubularmember iiicommunicating relation with said chamber to producehigh,,velocity discharge of said fluid, and means including a normallysolid, bonding material having a relatively low melting point responsiveto. the transfer of heat from said propellent fluid ,to said nozzle forrendering said securing means ineffective, whereby said nozzle will befree to drop clear of said tubular member.

4. In a jet propelled device the combination including, a tubular memberdefining a cylindridly tapered outlet for the gases liberated by thecombustion of said propellent material, an outwardly tapered Venturinozzle, and means for separably securing said nozzle to said tubularmember with the small end thereof aligned with said tapered outlet forexpending said gases, said nozzle being proportioned to expand saidgases to a temperature and pressure such that said flash inhibitingingredient will be effective in reducing the flash, said last mentionedmeans including metallic means having a low melting point for releasingsaid nozzle from said tubular memberafter combustion of said materialhas been completed.

5. A rocket projectile comprising, in combination, a ;tubular memberdefining a combustion chamber adapted to contain a material combustibleto generate a hot propellent fluid under pressure, said tubular memberhaving a rearwardly opening exhaust passage communicating with saidcombustion chamber, a plurality of arms secured in spaced relationshipto the periphery of'said tubular member and projecting rearwardlytherefrom, air fin means secured to said arms, a nozzle-for exchangingthe energy force of the propellent fluid, and bonding means securingsaid nozzle to said tubular member in communicating relation with saidexhaust passage, said arms cooperating with said nozzle in its securedposition to provide lateral support therefor, said bonding means beingrendered ineffective upon the application of heat thereto, whereby saidnozzle is frgedfrom said tubular member upon the combustion of saidmaterial.

6. In a jet propelled device, a cylindrical member defining a combustionchamber and having a rearwardly, inwardly flared entrance portion,

a nozzle having a constricted throat portion and a rearwardly, outwardlyflared exit portion, a propellent charge mounted in said chamber, meansfor detachably securing the constricted throat portion of said fio' zzleto said entrance portion of said combustion chamber, said securing meansincluding a low melting point metal for rendering ineffective saidfirst-mentioned means upon application of heat of a predeterminedtemperature generated by combustion of said propellent charge.

7. In a jet propelled device, a cylindrical member defining a combustionchamber and including a rearwardly, inwardly flared entrance portion, anozzle including, a constricted throat portion and a rearwardly,outwardly flared exit portion, a propellent charge mounted in saidchamber, means for detachably securing the constricted throat portion ofsaid nozzle to the entrance portion of said combustion chamber, saidsecuring means including complementary undercut portions on saidentrance portion and on said constricted throat portion inclined to theaxis of said cylindrical member, the undercut portion on saidconstricted throat portion being held against the undercut portion ofsaid entrance portion by the pressure generated by combustion of saidpropellent charge and exerted on the flared exit portion of said nozzle,said securing means being rendered ineifective'upon cessation of apredetermined pressure generated by combustion of said propellentcharge.

8. In a jet propelled device, a cylindrical member defining a combustionchamber and including a rearwardly, inwardly flared entrance portion, anozzle including a constricted throat portion and a rearwardly,outwardly flared exit portion, a propellent charge mounted in saidchamber, means for detachably securing the constricted throat portion ofsaid nozzle to the entrance portion of said chamber, said securing meansincluding a metallic bonding means having a relatively low melting pointfor rendering inefiective said first-mentioned means only uponapplication of heat of a predetermined temperature and upon cessation ofa--predetermined pressure generated by combustion of said propellentcharge.

9. In a jet propelled device, a cylindrical member defining a combustionchamber, a propellent charge mounted in said chamber, a nozzle, meansfor detachably securing said nozzle to said cylindrical member toprovide for expansion of the high velocity gases produced by combustionof said propellent charge, said securing means including complementaryundercut end-portions on said cylindrical member and on said nozzle anda low melting point material therebetween for rendering inefiective"said first-mentioned means only upon substantial completion of thecombustion of said propellent charge.

10. In a jet propelled device the combination of a cylindrical memberdefining a combustion chamber, a propellent charge mounted in saidchamber, a nozzle, fin supporting structure affixed to said cylindricalmember, means for de-' tachably securing said nozzle to said cylindricalmember to provide for expansion of the high velocity gases produced bythe combustion of said propellent charge, said securing means comprisingcomplementary undercut portions in said cylindrical member and in saidnozzle at the point of their contact and a low melting point metaltherebetween for rendering ineffective said first-mentioned means uponstoppagesof flow of said high velocity gases after substantialcompletion of combustion of said propellent charge.

11. The apparatus according to claim 10 wherein said propellent chargeincludes a flash inhibitor of the group consisting of potassium nitrate,barium nitrate, hydrocellulose and abietates, and wherein said nozzleextends beyond said fin supporting structure whereby said flashinhibitor is rendered substantially more effective without adverselyaffecting the ballistic properties of said device during its freeflight.

12. The apparatus according to claim 10 wherein a plurality of finmembers are pivotably supported by said fin supporting structure.

13. The apparatus according to claim 10 wherein said fin supportingstructure is streamlined.

14. In a jet propelled device the combination of a cylindrical memberdefining a combustion chamber and including a rearwardly, inwardlyflared entrance portion, a nozzle including a constricted throat portionand a rearwardly, outwardly flared exit portion, a propellent chargeincluding a flash inhibitor of the group consisting of potassiumnitrate, barium nitrate, hydrocellulose and abietates mounted in saidchamber to produce high velocity gases during combustion, a finsupporting structure fixedly attached to the entrance portion of saidcylindrical member, means for detachably securing said nozzle to therear end of said cylindrical member, said detachable means includingmaterial havin a low melting point for rendering ineffective saidfirst-mentioned means upon stoppage of flow of said high velocity gasesafter substantial completion of combustion of said propellent charge.

15. The apparatus according to claim 14 wherein the rearwardly,outwardly flared exit portion of said nozzle extends beyond said finsupporting structure whereby said flash'inhibitor is renderedsubstantially more effective without adversely affecting the ballisticproperties of said device during its free flight.

16. In a rocket component, a motor casing having a rearwardly-directeddischarge orifice, a Venturi nozzle, means detachably securing saidnozzle to said casing in cooperative relation with said orifice, saidmeans including a low melting point metal for rendering ineffective saidsecuring means to thereby release said nozzle from said casing inresponse to a predetermined temperature rise in said casing.

17. In a rocket motor component, a motor casing including a rearwardlydirected Venturi nozzle comprising a first inwardly and rearwardlyconstricted throat portion terminating in a second outwardly andrearwardly flared nozzle portion, said portions being discrete, meansreleasably securing said portions together, and further means responsiveto a predetermined temperature rise in said casing for releasing saidsecond portion.

18. The apparatus according to claim 17, wherein said last-named meansconsists of an alloy of relatively low melting point.

19. In a jet propelled rocket the combination comprising a cylindricalmember defining a combustion chamber having a rearwardly-directedentrance portion forming a discharge orifice, a nozzle having aconstricted throat portion, and means for detachably securing saidconstricted throat portion to said entrance portion, said entranceportion and said constricted throat portion each comprising a single,substantially Z- shaped undercut at the point of their respectivejuncture, said undercuts being complementary with respect to each other.

20. The apparatus according to claim 19 wherein the last-named means isrendered inoperable to release said nozzle from said member in responseto a predetermined temperature rise in said combustion chamber.

ELIOT B. BRADFORD. ALFRED AFRICANO. CLARENCE N. HICKMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,102,653 Goddard July 7, 19141,901,852 Stolfa et a1 Mar. 14, 1933 2,206,057 Skinner July 2, 1940FOREIGN PATENTS Number Country Date 305,160 Germany Mar. 3, 1920

